在下面的代码中，当我访问body参数中的map时，我遇到了一个问题，它将显示错误object？type can't be assign to widget？type，因此我在运行后将其用作Widget，我得到了我在这里询问的错误，因此如何在不得到这些错误的情况下访问widget（这里是构造函数）。

import 'package:flutter/material.dart';

import '../screens/categories_screen.dart';
import '../screens/favorites_screen.dart';

class TabsScreenBottom extends StatefulWidget {
  const TabsScreenBottom({Key? key}) : super(key: key);

  @override
  State<TabsScreenBottom> createState() => _TabsScreenBottomState();
}

class _TabsScreenBottomState extends State<TabsScreenBottom> {
  final List<Map<String, Object>> _pages = const [
    {
      'page': CategoriesScreen(),
      'title': 'Categories',
    },
    {
      'page': FavoritesScreen(),
      'title': 'My Favorites',
    },
  ];

  int _selectedPageIndex = 0;

  void _selectPage(int index) {
    setState(() {
      _selectedPageIndex = index;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Meal'),
      ),
      body: _pages[_selectedPageIndex]['page'] as Widget,
      bottomNavigationBar: BottomNavigationBar(
        backgroundColor: Theme.of(context).colorScheme.primary,
        selectedItemColor: Theme.of(context).colorScheme.secondary,
        unselectedItemColor: Colors.white,
        currentIndex: _selectedPageIndex,
        // type: BottomNavigationBarType.shifting,
        // giving animation when tab is changed
        onTap: _selectPage,
        items: [
          BottomNavigationBarItem(
            backgroundColor: Theme.of(context).colorScheme.primary,
            icon: const Icon(
              Icons.category,
            ),
            label: 'Categorey',
          ),
          BottomNavigationBarItem(
            // if your use type shifting
            backgroundColor: Theme.of(context).colorScheme.primary,
            icon: const Icon(
              Icons.star,
            ),
            label: 'Favorites',
          ),
        ],
      ),
    );
  }
}